Numerical control technology is a technology that controls mechanical movement and working process with digital information. Numerical control equipment is a mechatronic product formed by the infiltration of new technology represented by numerical control technology into traditional manufacturing industry and emerging mechanical processing manufacturing industry. Its technical scope covers many fields of manufacturing industry. It is the key equipment of modern manufacturing industry and the key equipment for enterprises to improve efficiency and competitiveness.

The correct operation and maintenance of CNC equipment is one of the key factors for the correct use of CNC equipment. Correct operation and use can prevent abnormal wear of the machine tool and avoid sudden failure; Routine maintenance can keep the equipment in good technical condition, delay the deterioration process, find and eliminate hidden faults in time, so as to ensure safe operation.

2. Problems that should be paid attention to in the use of CNC equipment

2.1 Operating environment of numerical control equipment

In order to improve the service life of CNC equipment, it is generally required to avoid direct sunlight and other thermal radiation, and to avoid places with too much humidity, dust or corrosive gas. Precision CNC equipment should be far away from equipment with large vibration, such as punch, forging equipment, etc.

2.2 Good power supply guarantee

In order to avoid the influence of large fluctuation of power supply (more than ± 10%) and possible instantaneous interference signals, the numerical control equipment generally adopts special line power supply (for example, one line is separated from the low-voltage distribution room for the use of numerical control machine tools) or additional voltage stabilizing devices, which can reduce the influence of power supply quality and electrical interference.

2.3 Formulate effective operation procedures

In the use and management of CNC machine tools, a series of practical and effective operating procedures should be formulated. For example, lubrication, maintenance, rational use and standardized shift system are the main contents of the use and management of CNC equipment. One of the important measures to ensure the safe operation of CNC machine tools is to formulate and abide by the operating rules. Practice has proved that many failures can be reduced by following the operating procedures.

2.4 Numerical control equipment should not be sealed for a long time.

After purchasing CNC machine tools, we should make full use of them, especially in the first year of putting them into use, so that the weak links that are prone to failure can be exposed as soon as possible and eliminated during the warranty period. During machining, the opening and closing of the spindle of the CNC machine tool shall be reduced as much as possible to reduce the wear of the clutch, gear and other devices. When there is no processing task, the CNC machine tool should be powered on regularly, preferably once or twice a week, and run for about 1 hour each time, so as to reduce the humidity in the machine by using the calorific value of the machine tool itself, so that the electronic components will not be affected with damp, and at the same time, it can timely detect whether there is an alarm for insufficient battery power, so as to prevent the loss of system setting parameters.

3. Maintenance of CNC machine tools

There are many types of CNC machine tools, which have different characteristics because of their different functions, structures and systems. The contents and rules of maintenance also have their own characteristics. The necessary regular and graded maintenance system should be formulated and established according to the type, model and actual use of the machine tool and the requirements of the machine tool manual. The following are some common and universal daily maintenance points.

3.1 Maintenance of CNC system

(1) Strictly abide by the operating procedures and daily maintenance system

Operators of CNC equipment should strictly abide by the operating procedures and daily maintenance system, and the technical and professional quality of operators is an important factor affecting the frequency of failure. When the machine tool breaks down, the operator shall keep the scene and truthfully explain the situation before and after the failure to the maintenance personnel, so as to analyze and diagnose the cause of the failure and eliminate it in time.

(2) Prevent dust and dirt from entering the inside of the numerical control device

Generally, there are oil mist, dust and even metal powder in the air of the machining workshop. Once they fall on the circuit board or electronic devices in the CNC system, it is easy to cause the insulation resistance between components to decrease, and even cause damage to components and circuit boards. In summer, some users open the door of the numerical control cabinet to dissipate heat in order to overload the numerical control system for a long time. This is an extremely undesirable method, which will eventually lead to accelerated damage to the numerical control system. They should try to reduce the opening of the doors of numerical control cabinet and strong electricity cabinet.

(3) Prevent system overheating

Check whether each cooling fan on the numerical control cabinet works normally. Check whether the air duct filter is blocked every six months or every quarter. If there is too much dust accumulated on the filter screen and it is not cleaned in time, the temperature in the numerical control cabinet will be too high.

(4) Regular maintenance of input/output device of CNC system

Most of the CNC machine tools produced before the 1980s were equipped with photoelectric tape readers. If the tape reading part was contaminated, it would lead to errors in reading information. For this reason, the optical reader must be maintained according to the regulations.

(5) Regular inspection and replacement of DC motor brush

Excessive wear of DC motor brushes will affect the performance of the motor, and even cause damage to the motor. For this reason, the motor brush should be checked and replaced regularly. CNC lathes, CNC milling machines, machining centers, etc. Should be inspected once a year.

(6) Regularly check and replace the storage battery

Generally, a rechargeable battery maintenance circuit is provided for the CMOS RAM memory device in the numerical control system to ensure that the contents of the memory can be maintained when the system is not powered on. Under normal circumstances, even if it has not failed, it should be replaced once a year to ensure that the system works properly. The battery shall be replaced under the power supply state of the numerical control system to prevent the information in the RAM from being lost during replacement.

(7) Maintenance of standby circuit board

When the spare printed circuit board is not used for a long time, it should be regularly installed in the CNC system for a period of time to prevent damage.

3.2 Maintenance of mechanical parts

(1) Maintenance of main drive chain

Regularly adjust the tightness of the spindle drive belt to prevent the loss of rotation caused by belt slippage; Check the constant temperature oil tank for main shaft lubrication, adjust the temperature range, replenish oil in time, and clean the filter; When the tool clamping device in the spindle is used for a long time, there will be a gap, which will affect the clamping of the tool, so it is necessary to adjust the displacement of the hydraulic cylinder piston in time.

(2) Maintenance of ball screw thread pair

Regularly check and adjust the axial clearance of the screw pair to ensure the reverse transmission accuracy and axial stiffness; Regularly check whether the connection between the lead screw and the bed is loose; If the protective device of the lead screw is damaged, it should be replaced in time to prevent dust or chips from entering.

(3) Maintenance of tool magazine and tool changing manipulator

It is strictly prohibited to load overweight and overlong tools into the tool magazine, so as to avoid tool dropping or collision between tools and workpieces and fixtures when the manipulator changes tools; Frequently check whether the zero position of the tool magazine is correct, check whether the tool change point of the machine tool spindle is in place, and adjust it in time; When starting the machine, the tool magazine and the manipulator shall be operated in an empty state to check whether each part works normally, especially whether each travel switch and solenoid valve can operate normally; Check whether the tool is reliably locked on the manipulator. If any abnormality is found, it shall be handled in time.

3.3 Maintenance of hydraulic and pneumatic systems

Regularly clean or replace the filter or filter screen of each lubrication, hydraulic and pneumatic system; Regularly test the oil quality of the hydraulic system, and add and replace the hydraulic oil; Regularly drain water from the water separation air filter of the air pressure system.

3.4 Maintenance of machine tool accuracy

Check and calibrate the machine tool level and mechanical accuracy regularly. There are two kinds of correction methods for mechanical accuracy: soft and hard. Its soft method is mainly through the system parameter compensation, such as the screw reverse clearance compensation, each coordinate positioning accuracy fixed point compensation, the machine tool returns to the reference point position correction and so on; Hard methods are generally carried out during the overhaul of machine tools, such as guide rail scraping, pre-tightening of ball screw nut pair, adjustment of reverse clearance, etc.

4 Concluding remarks

CNC equipment is a kind of advanced processing equipment with high degree of automation and complex structure. In order to give full play to the high efficiency of CNC equipment, it is necessary to operate correctly and maintain meticulously to ensure the normal operation and high utilization rate of the equipment. It integrates mechanical, electrical and hydraulic, so the CNC equipment has higher requirements for maintenance personnel. In addition to the routine maintenance mentioned in this article, specific special maintenance and maintenance should be carried out according to the detailed operation manual of the specific CNC equipment.